[BC] FM History

[Gary Peterson]

Richard,

I have to say that I always enjoy reading your posts.

There is one other characteristic of an electromagnetic wave that might lend
itself to modulation.  That is polarity.  I remember reading in an amateur
radio publication (decades ago) that someone was experimenting with
"polarity modulation."  The experiments involved something similar to FSK.
In this case, mark was horizontal polarization and space was vertical
polarization (or verse-visa).  The transmit and receive antennas (VHF or
UHF) were vertical and horizontal dipoles.  Of course, this would only work
on line-of-sight paths, as any long distance mode of propagation usually
randomizes the received polarization.

Regards,

Gary, KØCX
CE KFXS, KOUT, KKMK, KRCS, KKLS & KKBHB  

"The technology, i.e., the math probably goes back well before radio itself.
There are only two ways to convey information on a "wave." The most obvious
is varying the amplitude, and less obvious is varying the phase. FM is
"continuous phase." Of course, with modern digital transmission techniques,
combinations of both are used.
Richard B. Johnson"